1. Field of the Invention
The present invention relates to a resistance change memory in which data buses that connect cell arrays and sense amplifiers cross each other.
2. Description of the Related Art
In the readout system circuit of a conventional magnetic random access memory, a sense amplifier is arranged between two adjacent memory cell groups. The memory cell groups exclusively operate, thereby sharing the sense amplifier. Since the two memory cell groups share the sense amplifier, data buses are arranged on the left and right sides of the sense amplifier. Each data bus functions as a bus dedicated to the left or right array.
When a memory cell is selected in the readout operation of the readout system circuit, a reference cell is simultaneously selected. Memory cell data and reference cell data are transferred to the sense amplifier via the data buses. Let n be the number of bits to be read-accessed at once. In this case, n memory cell data buses and n reference cell data buses are necessary. Hence, 2n data buses are necessary on each side of the sense amplifier. This increases the data bus area in the chip size.
[Non-Patent Reference 1] “16 Mb MRAM Featuring Bootstrap Write Driver”, 2004 Symposium on VLSI Circuits, Digest of Technical Paper, pp. 454-457
[Patent Reference 1] U.S. Pat. No. 5,695,864